1. Field of the Invention
The present invention relates to a welding apparatus used in manufacturing automotive parts, such as strut mounts mainly used in vehicular front supports.
2. Related Art
There are strut mounts as automotive parts for front support employed on the front side of a vehicle. The strut mount is used in a strut-type suspension to couple the upper end of a piston rod of a shock absorber to a vehicular panel through an insulator rubber.
The strut mount 1 is structured, as shown in FIG. 8 and FIG. 9, by joining main-body metal fitting 2 as a case accommodating the insulator rubber (not shown) by press-fit means and cover metal fitting 3 serving also as a mount bracket through their flanges 2a, 3a. The flanges 2a, 3a are fixed to the vehicular panel through bolts and nuts. For this reason, the flanges 2a, 3a of the main-body metal fitting 2 and cover metal fitting 3 have a plurality of penetration-holes 5 formed at a required interval in a circumferential direction in order to mount to the vehicular panel.
In the manufacture of the strut mount 1, the main-body metal fitting 2 and cover metal fitting 3 accommodating the insulator rubber are joined together at their flanges 2a, 3a by the welding means, with the flanges 2a, 3a contacted with each other.
In the welding between the main-body metal fitting 2 and the cover metal fitting 3, so-called the resistance welding technique is adopted. In the welding, usually two metal plates are laminated to vertically apply pressure to a weld point by use of an electrode and great current is supplied for direct energizing so that the joining point between the metal plates can be heated up by occurrence of Joule""s heat. Simultaneously, great pressure is applied to the metal plates to weld them at their contact sides.
The related art weld process has used a welding apparatus having a lower electrode arranged on a support table to support a main-body metal fitting and cover metal fitting to be welded and an upper electrode arranged for vertical movement above that electrode. The support table has a plurality of positioning pins projecting therefrom that are to be fitted in the mounting penetration-holes of the flanges of the main-body metal fitting and cover metal fitting. In welding operation, main-body metal fitting and cover metal fitting are supplied one by one onto the support table. The penetration-holes are fit with the pin. to hold them with positioning in a lamination state. By descending the upper electrode, welding is made while clamping predetermined weld. points by the upper and lower electrodes. This operation is repeated to proceed welding.
In the meanwhile, the positioning pins and the penetration-holes of the main-body metal fitting and cover metal fitting to be fit therewith are formed with comparative accuracy in order to provide improved positioning accuracy and preferred quality of welding. Accordingly, when welding is once made by fitting the penetration-holes of the main-body metal fitting and cover metal fitting with the pins, the penetration holes at their peripheral edges are in engagement with the pins under the influence of welding heat or the like. This however makes it uneasy to manually remove them from the pins, resulting in impairing the operationality in welding.
It is an object of the present invention to provide a welding apparatus capable of welding two parts of component metal fitting to be joined in a state held in position and easily remove a welded part from a positioning pin through a simple structure as a welding apparatus used for welding two of metal fitting, such as main-body metal fitting and cover metal fitting in the manufacture of automotive parts, such as strut mounts, thereby improving operationality in welding.
A welding apparatus for achieving the above object is in a welding apparatus for positioning and welding two parts of component metal fitting formed with a plurality of penetration holes spaced in circumferential direction in manufacturing automotive parts, the welding apparatus having support tables to support two parts of component metal fitting to be welded, positioning pins provided standing on the support table in positions corresponding to a plurality of penetration holes possessed in the two part of component metal fitting and to be fit with the penetration holes, a lower electrode provided to support the two parts of component metal fitting at joining portions thereof, and an upper electrode vertically movably provided in an upper position corresponding to the lower electrode, the positioning pin having an upper end formed in a tapered form, the pin being supported to be elastically pressed down by spring means, the tapered upper end being to be pressed down from a projection state in a position above the penetration hole of the part of component metal fitting held by the lower electrode, and urging means provided to press down the pin against the spring means separately from the upper electrode.
According to this welding apparatus, where welding two parts of component metal fitting formed with a plurality of penetration holes at an interval in the circumferential direction by use of this welding apparatus in manufacturing automotive parts such as strut mounts, the both parts of component metal fitting are supplied one by one to the support tables and the penetration holes possessed in them are fitted with the positioning pins possessed on the support tables to provide positioning and rested and stacked on the lower electrode possessed on the support tables.
At this time, the positioning pin is in a projecting state that the tapered upper end is above the penetration hole of the part component metal fitting supported by the lower electrode by spring means. The both parts of component metal fitting is accurately positioned and laminated by fitting the penetration hole with a lower portion of the tapered upper end of the positioning pin.
In this state, the upper electrode is descended to vertically clamp a predetermined joining point by the upper and lower electrodes. The both electrodes are energized to weld opposed surfaces of the laminated both parts of component metal fitting. When an automotive part completed of welding is recovered from the support table, urging means separate from the upper electrode is descended to press down the positioning pin against the spring means.
By this pressing down, the tapered upper end of the pin is pressed down to a position of the penetration hole of the part of component metal fitting or the below. As a result, even if the penetration hole at its peripheral edge and the pin are formed comparatively accurate and in an engagement state due to the influence of welding heat, the engagement is to be released. Accordingly, it is possible to easily take up and recover the automotive part completed of welding from the support table.
In the welding apparatus, a turntable is provided that intermittently rotates by a required angle per time, the support tables being mounted at a required interval in a circumferential direction on the turntable, the vertically movable upper electrode provided above one stop positions of the support table due to rotation halt of the turntable, the urging means for pressing down the positioning pin provided above one stop position of another one of the support table, the upper electrode descending to carry out welding and the urging means descending at a halt of rotation thereof correspondingly to the intermittent rotation of the turntable.
Due to this, two parts constituting welding automobile parts are supplied one by one to a plurality of support tables on the intermittently rotating turntable on the basis of each support table in a predetermined stop position and positioned by fitting respective penetration holes with the positioning pins, supported by the lower electrode. The upper electrode descends from the above in a stop position of one support table at a halt of rotation correspondingly to the intermittent rotation of the turntable to cooperate with the lower electrode on the support table, clamping and welding the two welding parts of component metal fitting. In a stop position of another support table, the urging means descends to press down the positioning pin against spring means thereby making possible to disengage the pin from the part of component metal fitting. Accordingly, welding operation for strut mount metal fitting can be successively made. Automation is easy and the operation efficiency of welding can be improved. Also, even for those to be successively welded, the welding apparatus is not excessively increased in size, thus suppressing increase of installation space.
Furthermore, the turntable is provided intermittently rotatable by 90 degrees per time, the support tables being mounted at a positional interval of 90 degrees in the circumferential direction on the turntable, the upper electrode being provided above one stop position of the support table, the urging means being provided above a stop position opposite thereto. In this case, the efficiency of welding operation and space saving are made further effective.